This invention relates to the field of zeolites and their use in detergent formulations. In particular, it relates to zeolites coated with anionic functional organosilicon compounds. The coated zeolite has improved properties making it more useful in detergent formulations.
Zeolites are well known ion exchange agents that have been used recently to replace all or part of the phosphates in several detergent formulations. However, the use of zeolites in detergents has generated several problems. In particular, the zeolites tend to agglomerate during industrial preparation of detergent formulations. It has been suggested that the agglomeration results from the interaction of the zeolite with other detergent ingredients during the spray drying process. These agglomerates deposit on the fabric being laundered and are especially noticeable as white particulate material on dark fabrics.
Alkali metal silicates have been implicated as one of the components of detergents that may interact with zeolites to cause the agglomeration. Consequently, it has been proposed that only limited amounts of silicate, 3% or less, should be used in zeolite built detergents. Larger amounts of alkali metal silicate have been shown to decrease the ion exchange capacity and the rate of ion exchange of the zeolite in the detergent. Soluble silicates, however, are valuable components in detergent formulations for their bead formation, anticorrosion and other functions that make detergent processing and use easier.
U.S. Pat. Nos. 4,138,363, 4,216,125 and 4,243,545 teach that the tendency of zeolites to agglomerate during detergent processing can be reduced by treating the zeolite surface with a hydrophilic functional silane. While acrylates, epoxies, amines and carboxylates are suggested as useful hydrophilic groups, the only silanes taught for treating the zeolite were beta-3,4-epoxycyclohexyl-ethyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane and gamma-aminopropyltrimethoxysilane. However, the improvements achieved with these silane-zeolite composites has not been sufficient to result in commercial utilization.
Consequently there is still a need for a commercially viable way of modifying zeolite so that it can be incorporated in soluble silicate containing detergent formulations without agglomeration problems. Furthermore, it is important that the zeolite can be incorporated into the detergent formulation without reducing its ion exchange properties. Accordingly, it is a purpose of the present invention to provide an improved method of modifying the properties of zeolite so that it can be incorporated into soluble silicate containing detergent formulations without producing agglomerates that deposit as white particulate material on fabric during laundry. It is a further object of the present invention to provide a zeolite that retains its capacity and rate of ion exchange when formulated in a detergent containing substantial amounts of alkali metal silicates.